The invention relates to a method for the separation of a mixture of plastics. More particularly, it is directed to a method for separating flakes of polyvinyl chloride (PVC) from flakes of polyethylene terephthalate (PET) by the application to the flakes of a solution composed of a low density solvent of PVC, water (H.sub.2 O) and sodium hydroxide (NaOH).
For many years there has been the problem of separating different kinds of plastics which have been mixed together in a recycling situation. Usually, plastic bottles made of various types of plastics are brought to recycling stations where they are ground into flakes. Quite often, the bottles are not separated according to the plastic of which they are composed before they are ground into flakes. As a result of this practice, flakes of different plastics are randomly mixed together. The separation of these flakes becomes difficult when the physical properties of the plastics make separation by standard flotation and melting techniques impossible. Two such plastics with almost identical physical properties are PVC and PET. PVC and PET are the primary types of plastics used in the production of plastic bottles and other containers. It is important to recover these plastics by recycling in order to preserve the environment, conserve energy and reduce cost.
Previous prior art methods of separating a mixture of plastics can be found, for example, in U.S. Pat. Nos. 3,925,200; 3,926,790; 3,926,791; and 4,132,633. These prior art references disclose the general concept of separating a mixture of plastics by flotation after a conditioning agent has been added to the mixture.
The present invention provides for an improved method of separating particles or flakes of PVC from particles or flakes of PET.